The invention relates to a coupling for coupling two rotatable bodies, in particular a gear and a drive shaft which are disposed essentially concentric to each other, with or without an axial offset, having a coupling part. The invention also relates to a fuel-supply pump with two rotatable gears that engage each other and are disposed in a pump chamber, which supply fuel from an intake chamber connected to a storage chamber, along a supply conduit constituted between the end faces of the gears and the circumference wall of the pump chamber, into a pressure chamber, wherein one of the gears is driven by a drive shaft.
The coupling of two rotatable bodies can take place, for example, by means of a cross notched coupling, which is also known as a cross-staff or Oldham coupling. Couplings based on the cross notch principle are used to transmit movements. They are predominantly used for drive coupling when axes are not in alignment.
The cross notch principle is based on two coupling halves (driving and driven) and an intermediary disk as a coupling part. Guide strips or guide grooves that are disposed perpendicular to each other are embodied on both coupling halves. Complementary guide grooves or guide strips are embodied on the intermediary disk. The transmission of the rotary movement occurs in an equiangular manner, wherein the intermediary disk slides against the guides of the coupling halves.
The known cross notch principle is based on a series connection of a driving element, an intermediary disk, and a driven element. The transmission of a torque occurs in two planes. This results in a relatively large structural height. In addition, the tilting inclination of the intermediary disk has turned out to be disadvantageous. The occurrence of a large surface pressure in the guides at high speeds leads to an intense development of frictional heat and a high degree of abrasion.
The object of the invention is to produce a coupling that functions according to the cross notch principle and a fuel-supply pump with a coupling of this kind that has a small structural height and a long service life. The coupling according to the invention and the fuel-supply pump according to the invention should be inexpensive to produce and easy to assemble.
In a coupling for coupling two rotatable bodies, in particular a gear and a drive shaft which are disposed essentially concentric to each other, with or without an axial offset, having a coupling part, the object is attained by virtue of the fact that the coupling part is integrated into one of the rotatable bodies. As a result, connecting shafts and captive retentions that are required in conventional couplings can be eliminated. This leads to a reduction in the number of required parts. In addition, a pre-centering of the rotatable bodies is possible with the aid of the integrated coupling part. The coupling part can be comprised of one or several parts.
A particular embodiment of the invention is characterized in that the coupling part is embodied as intrinsically asymmetrical. This has the advantage that it prevents an incorrect installation of the coupling part. This simplifies the assembly.
Another particular embodiment of the invention is characterized in that the contact surfaces between the coupling part and the rotatable bodies are embodied as convex. As a result, the surface pressure occurring during operation is reduced and the lubrication properties are improved. The attendant friction and therefore abrasion are minimized.
Another particular embodiment of the invention is characterized in that the coupling part has the form of a disk, which has a central oblong hole with approximately planar or slightly convex side surfaces let into it that serves to receive the one rotatable body, in particular a drive shaft, and which has four tapering projections embodied on it, wherein a central recess is provided in the other rotatable body, in particular a gear, whose contour is embodied as complementary to the contour of the disk. Usually, the coupling is disposed outside the function chamber. Through the embodiment of the coupling according to the invention, it is possible to dispose the coupling inside the function chamber. The function chamber can, for example, be the housing of a fuel-supply pump.
In a fuel-supply pump with two rotatable gears that engage each other and are disposed in a pump chamber, which supply fuel from an intake chamber connected to a storage chamber, along a supply conduit constituted between the end faces of the gears and the circumference wall of the pump chamber, into a pressure chamber, wherein one of the gears is driven by a drive shaft, the above-explained object is attained by virtue of the fact that the drive shaft is coupled to the driven gear by means of a coupling described at the beginning. A fuel-supply pump of this kind has been disclosed, for example, by DE 196 25 488, U.S. Pat. No. 6,050,795, the disclosure of which is hereby incorporated by reference. The fuel-supply pump is driven, for example, by means of the camshaft of an internal combustion engine. The fuel-supply pump can also be coupled to a high-pressure pump. The fuel-supply pump according to the invention has the following advantages: coupling of the gear to the drive shaft in only one plane, fewer points of intersection, a smaller tilting inclination, less intense tilting moments, lower friction, smaller structural height, fewer parts, optimized materials utilization, weight reduction, integration of the coupling part into the driven gear, no additional recess or guide required for the coupling part, integrated lubrication, integrated cooling, inexpensive and efficient manufacture using sintering technology, plastic injection molding technology, or punching technology, possible pre-centering during assembly, improved damping, prevention of incorrect installation of the coupling part by means of asymmetrical geometry, clockwise and counterclockwise travel with uniform transmission behavior, possible clockwise and counterclockwise travel with different transmission behaviors, reduced surface pressure due to convex or concave contact geometry, and elimination of captive retention through subassembly integration.
Other advantages, features, and details of the invention ensue from the following description in which various exemplary embodiments of the invention will be described in detail in conjunction with the drawings. The features mentioned in the claims and in the specification can be essential to the invention individually or in arbitrary combinations.